During the drilling of a wellbore, various fluids are used in the well for a variety of functions, The fluids may be circulated through a drill pipe and drill bit into the wellbore, and then may subsequently flow upward through wellbore to the surface. During circulation, a drilling fluid may act to remove drill cuttings from the bottom of the hole to the surface, to suspend cuttings and weighting material when circulation is interrupted, to control subsurface pressures, to maintain the integrity of the wellbore until the well section is cased and cemented, to isolate the fluids from the formation by providing sufficient hydrostatic pressure to prevent the ingress of formation fluids into the wellbore, to cool and lubricate the drill string and bit, and/or to maximize penetration rate.
Water-based drilling fluids are often selected for use in a number of hydrocarbon plays, because of the lower associated cost and increased environmental compatibility as compared to oil-based drilling fluids often thought to be the first option in drilling operations. However, other concerns beyond cost effectiveness may also be involved in the selection of wellbore fluids, such as the type of formation through which the well is being drilled. For example, subterranean formations may be at least partly composed of reactive clays, including shales, mudstones, siltstones, and claystones, that swell in the presence of aqueous fluids. While drilling in clay-containing formations, operators may encounter a number of problems encountered that may include bit balling, swelling or sloughing of the wellbore, stuck pipe, and dispersion of drill cuttings into the surrounding wellbore fluid.